The world's highest navigable body of water will take your breath away - quite literally, as it lies at a staggering 3856m above sea level.
Lake Titicaca was the most sacred lake in the Incan Empire. The Incas believed it was from these deep, cold waters that Manco Capac, their first king, sprang - along with his sister and consort, Mama Ocllo. The pair founded the city of Cusco (a day's journey in the 21st century, with a range of bus operators covering the ground for about $60) as capital of the Incan Empire.
The suyu, or region, that encompassed Lake Titicaca was of prime importance to the Incas for its gold and silver mines, the breeding of alpacas and llamas for meat and wool, and the ability to farm potatoes, coffee and quinoa (a type of grain), despite the altitude.
Although the familiar monuments of the Inca era are concentrated in the Sacred Valley beyond Cusco, Lake Titicaca has a depth of history and intrigue matched by few other locales in South America.
Remind me where it is
Lake Titicaca is located at the northern end of the Altiplano basin, high in the Andes.
It is the second-largest lake in South America, (after Lake Maracaibo in Venezuela), with an impressive surface area just less than half the size of Wales. It is shared by Bolivia and Peru, with the latter possessing the bigger portion.
Once considered unfathomable, the lake has now been measured as about 280m deep. It hosts more than 60 species of birds, including flamingos, the Andean flicker and the Titicaca flightless grebe, which is endemic to the Titicaca basin and in danger of extinction.
More than two dozen rivers feed the lake; rainfall and melt-water from the glaciers on the sierras of the Altiplano help to top it up.
Where do I start?
Even though the most interesting shore and hinterland are in Peru, the Bolivian capital, La Paz, provides the easiest gateway to Lake Titicaca. You can reach the lake without going into La Paz itself: from the airport, a shared minibus to the suburb of El Alto should cost a few cents; ask to be dropped off on the road, where you can pick up a bus to Copacabana, for about $15.
This is one of the most entertaining journeys in South America, since it involves a water crossing - possibly your first encounter with Lake Titicaca - across the Strait of Tiquina to the peninsula on which Copacabana stands. At the shore, all the bus passengers are off-loaded on to launches while the bus is floated across on a precarious-looking low wooden barge, one of which is named Titanic.
Back on the bus, the final stretch of the journey is a dramatic climb through the hills, with excellent views of the lake, before descending to the town whose name, Copacabana, has nothing to do with Barry Manilow's disco ditty.
This colourful town is a strange combination of austere high Andes and beachside resort - it is, after all, the closest that landlocked Bolivia gets to a seaside. Primary-coloured pedalos, some in the shape of giant swans, line a beach that sweeps between the two hills Cerro Calvario (Calvary Hill) and Cerro Nio Calvario (Little Calvary Hill).
Stop at one of the restaurants along the beach to try Titicaca trout with a cold Pacea beer and admire the gem-like quality of the lake.
At the weekend, you can witness Cha'lla outside the town's church. This is a ritual blessing of vehicles, when cars, buses and trucks are decked with bright garlands of plastic and fresh flowers, ribbons and flags as their owners petition the Virgin for protection, while dousing their vehicles with alcohol.
For a dollar or so, a taxi will take you the few kilometres from Copacabana to the Peruvian border.
Formalities are slow, but relaxed and friendly at this frontier, and on the far side minibuses and shared taxis wait for the short journey to Yunguyo. From this attraction-free town, buses take about three hours to reach Puno - effectively the capital of Lake Titicaca.
Puno sits on a bay at the northwest end of the lake. It is a sprawling, labyrinthine and confusing city, but it is friendly, steeped in tradition and a centre of Peruvian folklore.
Many tour operators run trips of a day or two on the lake, in which you discover some of its dozens of islands. You could be collected at dawn from your hotel by the reliable Kollasuyo Tours, to be taken to the scruffy port west of central Puno. Here, you board your boat for a gorgeous day trip to the fascinating island of Taquile and the floating reed islands of Los Uros.
The 21/2-hour, 35km journey to Taquile is accompanied by an English-speaking guide with tales of the lake, its inhabitants and history.
When you arrive at the tiny port, navigate the gruelling 525 steps to reach the intimate main plaza, the highest point of the island.
The steep sides of this whale-shaped island are dramatically lined with ancient terracing that dates back to AD500. Its rich soil is as red as the sun-scorched cheeks of the Taquileos, who still use foot-ploughs little altered since Inca times.
Taquile has been inhabited for 10,000 years and is today home to a community of weavers (men and women) and knitters (just men) of fine alpaca wool.
Refuel before leaving the island with lunch served in an islander's home - a tasty menu of grilled kingfish from the lake with native potatoes and quinoa - included in the price of the day trip. The standard tour then takes you to the man-made, floating Islas de Los Uros, constructed entirely from the abundant tortora reed.
The Uros Indians traditionally resided on artificial islands to avoid the aggressions of the Incas and Collas. There are more than 30 islands in total, but only a handful can be visited by tourists.
The women bound across the spongy surface of the reeds to offer tapestries and handicrafts for sale. They dress in embroidered blouses above many-layered, bright skirts: an oversized bowler hat crowns the creation, a fashion imported from Britain in the 19th century.
Can I meet the Incas?
After a fashion. Another excellent day-trip from Puno is to Sillustani, an ancient burial site on the much smaller Lake Umayo.
Though some way from Lake Titicaca, it is worth exploring because of its significance as a pre-Incan burial ground and its electrifyingly beautiful, yet serene setting.
The hillside is dominated by a series of strange, round towers called challpas, burial places for the Colla people. As the Incan Empire expanded in the 14th century this culture was absorbed, but gave its name to the southern quarter of the empire, Collasuyo.